Printing press and method



June 23, 1964 C. c. HARRIS ETAL 3, 38,097 PRINTING PRESS AND METHOD Filed March 14, 1962 2 Sheets-Sheet l 4o 32 FlG-3 2 551 2 55 i 5rz u u I 22a 22b 20 2 25a. 25b F|G-4 H INVENTORS CHARLES C. HARRIS & 4- BY ROBERT K. NORTON WM m fw ATTORNEYS June 23, 1964 Filed March 14, 1962 C. C- HARRIS ETAL PRINTING PRESS AND METHOD 2 Sheets-Sheet 2 E +o5o E LIGHTFBRM +.o25:\

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||||m| ||||1||| IIIIIIIIIHI llll I! PRINT LENGTH VARIATION PLATE PLUS PACKING I NVEN TORS CHARLES c. HARRIS a BY ROBERT K. NORTON ATTORNEYS United States Patent 3,138,097 PRINTING PRESS AND METHOD Charles C. Harris, Chagrin Falls, and Robert K. Norton,

Twinsburg, Ohio, assignors to Harris-lntertype Corporation, Cleveland, fihio, a corporation of Delaware Filed Mar. 14, 1962, Ser. No. 179,588 7 Claims. (Cl. 101-216) This application relates to printing presses, particularly to improvements in rotary letterpress adapted to use relatively thin flexible plates, especially a plurality of such plates on the plate cylinder.

In connection with recent commercial developments in the rotary letterpress field, there exists a need for such presses capable of printing from a plurality of thin flexible plates, for example, etched plates having a rather shallow relief. In one type of application, two or more plates may be mounted on the plate cylinder of the press in sideby-side relation, extending around the plate cylinder the full active peripheral distance, in other words from the leading edge clamp to the trailing edge clamp. The plates being side-by-side are thus often referred to as a split plate arrangement.

In such applications these plates ordinarily print the same color, unless a split fountain is used, but the image area of each of the plates may be substantially different. For example, one plate may be a heavy form, having an image containing large solids, and thus a substantial portion of the plate will contact the inking apparatus and the sheet upon which the plate is to be made, whereas another plate on the same cylinder may be a light form, having a relatively light image area, for example, a halftone image or a few or scattered lines of script matter, and thus contact of the image area of this plate with the inking apparatus and the material to be printed will be in comparison rather slight. As a result, a condition occurs which is known in the art as a difference in the length of print between the printed areas on the material produced by the different heavy and light forms. The print is referred to as being long or short depending on its relation to the normal, desired print length.

As an explanation of the apparent causes of printing long or short, it might be said that where a very light form is printed with but a very small area of printing at both the leading and trailing edges of a sheet, the image length will print fairly true since the sheet will be relatively static regarding external stresses, for almost all of the time it is passing around a printing cylinder. Now, taking the other extreme, if a sheet is printed solid and under pressure from its leading to its trailing edges, the sheet will tend to be ironed out and stretched to some degree during the ironing process. While this occurs, however, the plate image length will remain constant. When the pressure on the ironed sheet is released, the sheet will tend to snap back to almost its original condition and its image will snap back accordingly. It will be seen therefore, that the resultant image on the paper will be shorter than the actual image on the plate. Any degree of plate image area between these two extremes will, of course, tend to effect corresponding printed image length changes. An example somewhat analogous to the above might be said to be the printing of a rubber balloon with a rubber stamp. If the balloon is stamped while it is relaxed, the printed image length should be the same as the image length on the rubber stamp. If the balloon Patented June 23, 1964 is enlarged fully and then stamped, the resultant printed image, when the air is released from the balloon, will be shorter than the length of the rubber stamp image. Any degree of pressure in the balloon between the two extreme conditions will result in a printed image length which corresponds to the amount of stretch of the rubber of the balloon. While this example is not completely accurate, it is suitable to explain a primary cause of change in print length due to image area diflerences.

The principal object of this invention is to provide a method and apparatus which enables relief printing from a thin, flexible printing plate or plates, in which laterally adjacent printing surfaces of the plate or plates mounted on a plate supporting member may be arranged at different heights to compensate for print length dilferences resulting from dififerent plate image areas on the adjacent surfaces.

A more specific object of this invention is to provide a method and apparatus whereby the length of print from different thin letterpress plates having a significantly different percent of image to non-image printing area and mounted on the same plate cylinder can be compensated for independently, and resultant prints of desired length can be obtained from each, thus facilitating printing from one printing unit by a plurality of plates having significantly different image areas.

Another important object of this invention is to provide, in a rotary letterpress, mounting apparatus for a plurality of flexible relief plates, whereby the length of print produced from each plate on a common plate cylinder can be controlled to equalize, or adjust into register with other prints, the length of print from each plate in spite of significantly different extent of image areas on the different plates.

Another object of this invention is to provide a novel method of letterpress printing from a plurality of flexible relief plates which, in spite of significantly different areas of images they produce, can be mounted on the same plate cylinder in side-by-side relation, and made to print images of controlled length, whether equal or unequal, within certain tolerances.

, Another object of the invention is to provide a novel method of letterpress printing in which a plurality of plates are mounted on a common plate carrying member and the entire image areas on different plates are raised or adjusted to different heights than each other whereby control is exercised over the length of print obtained from the respective plates.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings:

FIG. 1 is a schematic representation of a typical rotary letterpress, to which the present invention is applicable.

FIG. 2 is an enlarged schematic view showing the engagement between the inking cylinder and the plate cylinder, with the latter having a pair of flexible relief plates mounted thereon;

FIG. 3 is a view similar to FIG. 2 looking into the nip between the plate cylinder and the impression cylinder;

FIG. 4 is a diagram showing the differences in the length of print obtained from plates having significantly different image areas;

FIG. 5 is a somewhat schematic view on a greatly enlarged scale, taken transversely of the nip at which a 3 light form plate is engaging a sheet of print receiving material carried on the impression cylinder;

FIG. 6 is a view similar to FIG. 5, showing the same relationship with respect to a heavy form plate;

FIG. 7 is an enlarged sectional view taken along the nip between the inking and plate cylinders, and showing the manner in which the split plates are inked according to the invention;

FIG. 8 is a view similar to FIG. 7, taken along the nip between the plate cylinder and the impression cylinder, and illustrating the manner in which compensation is ordinarily made for the difference in image areas between the split plates; and

FIG. 9 is a graph illustrating example dimensions of packing beneath typical flexible relief plates in order to achieve the adjustment of print length according to the invention.

Referring to the drawing, which illustrates a preferred embodiment of the invention, and particularly to FIG. 1, a printing press is shown in the form of a letterpress adapted to print from thin flexible relief plates. The press includes a sheet feeding mechanism shown schematically at 10 which supplies individual sheets of print receiving material 11 (such as paper) to an impression or tympan cylinder 12. Of course, in the case of a web press this feeding mechanism would be replaced by conventional means for directing a web of paper or the like to the impression cylinder. For purposes of description, however, reference hereinafter will be made to a press for printing on individual sheets. Each sheet 11 is appropriately gripped at its leading edge by gripper means 14 in the form of conventional pivotally mounted fingers which are controlled from known mechanisms to engage the leading edge of the sheet in timed relation to its feeding motion, and to hold the leading edge of the sheet securely on the impression cylinder 12 during the printing operation. The active surface of the impression cylinder, i.e., that surface against which the sheet rests, is covered by one or more tympan sheets 15.

Cooperating with the impression cylinder is a plate carrying member which in a rotary press takes the form of a plate cylinder 20, driven in counter-rotating relation therewith and at the same angular speed. This cylinder includes clamps shown schematically at 22 which engage the leading and trailing edges of thin flexible relief plates 25, such plates being, for example, from about .010 inch to .040 inch thick. The invention is particularly concerned with arrangements for mounting a plurality of such plates on the cylinder 20, and thus (referring to FIG. 2) two plates 25a and 2512 are shown. Each plate is engaged at its leading and trailing edges by separate individually adjustable clamping members, designated 22a and 22b, respectively, which can be of any conventional type used for grasping and tensioning the plates. Therefore, each plate can be mounted, positioned, and tensioned independently of the other. Of course, it may be desirable to provide mountings, and therefore separate clamps, for more than two plates.

The impression cylinder 12 and plate cylinder provide between them a printing nip 28 through which the sheets 11 are carried to transfer ink in the form of an image from the plates and 25b onto the sheets. Upon leaving this hip, the printed sheet is then carried on the impression cylinder to conventional delivery mechanism 30, including grippers in the form of fingers 32 carried on the chains 33 of the delivery mechanism. These grippers, as is known in the art, are operated to take the printed sheet from the gripper means 14 on the impression cylinder and carry the sheets to a device for stacking the printed sheets, etc., or to the next printing couple in a multi-color press. A printed sheet 11 is shown engaged with the lowermost delivery grippers 32, and extending around the cylinder 34 of the delivery mechanism with the trailing edge of this sheet still partially in contact with the tympan sheet on the impression cylinder.

The plates 25a and 25b are inked by an inking apparatus which, briefly, includes an inking cylinder 38 commensurate in size with the plate cylinder 20 and counterrotating with respect thereto at the same angular speed. The cylinder 38 is provided with a resilient inking member, preferably in the form of a replaceable blanket 40 of rubber or equivalent material, this blanket being fastened to the cylinder 38 by conventional leading and trailing edge clamping mechanisms 42. Ink is supplied uniformly to the surface of the inking blanket 40 by an inking apparatus, designated by the general reference numeral 45, and including a plurality of inking rollers 46 which contact the blanket member 40. Details of a preferred form of this apparatus are shown and described in United States Patent No. 2,448,975, issued September 7, 1948, to Harrold and Meyer.

Thus, the inking and plate cylinders form between them an inking nip 48 across which there is a relatively narrow band (in most cases discontinuous according to the relief of the plate or plates) of contact between the resilient inking member 40 and the plates 25a and 25b. The contact pressure by which ink is transferred from the member 40 to the plates is precisely controlled by apparatus which determines the compression of the resilient member 40 against the plates. These cylinders are provided with contacting bearers 50 and 52 at opposite ends thereof, the bearers being maintained in contact under pressure during printing operation. The relieved nonimage areas of the plates may be only slightly relieved with respect to the image or printing areas of the plate. For example, relief in the order of 0.005 to 0.016 inch may be employed, and the compression of the inking member 40 still maintained effective completely and fully to ink the image areas of the plate.

As mentioned in the introduction to this application, one of the printing plates may have predominantly nonimage areas, while the other plate may have a predominance of image areas, or at least a significantly greater proportion of image area than the one plate. For purposes of illustration, therefore, plate 25a is shown with more widely spaced cross-hatching and will be understood to represent a plate having the relatively lesser image area, known also in the art as a light form. Plate 25b is illustrated with closer spaced cross-hatching, and will be understood to represent a plate having significantly greater image area, also referred to in the art as a heavy form.

The plate 25a, therefore, in spite of the fact that it has the same length around the plate cylinder and the same height of image areas above its base as the plate 25b, will tend to print long or in other words produce an image on the sheet material which is longer front to back, that is, in the direction of the sheet as it is wrapped around the impression cylinder, while the plate 25b, the heavy form, will tend to print short.

Assuming for purposes of illustration that the bearers 52 are raised or extend radially outward from the surface of the plate cylinder, for a distance of approximately 0.038 inch, then the normal or standard packing employed between the plate and the surface of the plate cylinder would be sufficient to bring the total thickness of the plate plus packing to 0.038 inch. For purposes of understanding the invention this dimension may be taken as typical and illustrative of standard plate packing to bearer height. If the light form (plate 25a) is packed this amount it will produce a print which is significantly longer from front to back than the heavy form plate 25b packed to the same height. However, if the packing beneath the plate 25a is increased in thickness and the packing between the heavy form plate 25b is decreased, the length of print from each of these plates can be adjusted to coincide or register. In this manner, according to the method of this invention it is possible to control the length of print of heavy forms and light forms mounted in so-called split plate relationship on the same plate cylinder, and to adjust the length of print from each plate to register with other prints of different colors, to register with each other in some cases, or to correspond to a predetermined print length dictated by subsequent cuts to be made of the print receiving material, for example, as by a cutter and creaser.

Since the pressure of the resilient inking member or blanket 40 against the plates must be carefully controlled to provide uniform inking of the image areas and to avoid deposit of ink in the slightly relieved non-image areas, the packaging underneath blanket member 40 must be increased or decreased proportionately, the inking member being packed up where it inks the light form plate 25a, since this plate is underpacked, and the inking member being underpacked with respect to the overpacked heavy form plate 25b. It will be understood by those skilled in the art that this result may be obtained in a variety of different Ways. The drawings disclose a preferred construction wherein the inking member is one continuous blanket 40, and packing of different thickness, either integral sheets of packing having a different thickness or a different number of sheets of uniform thickness, being used to raise certain areas of the inking blanket higher (with respect to the surface of the inking cylinder) than other areas. Of course, it is possible to use a split blanket in other Words two or more blankets of different thickness according to the required raising or lowering of appropriate areas of the blanket, but this in turn would require separate clamping mechanisms for tensioning each of these several parts of a split blanket. The preferred and least complicated arrangement is believed to be that shown in the drawings.

As a result of the relatively different packing of the plates 25a and 25b, it will be recognized by those skilled in the art that if the impression cylinder is provided with a tympan sheet of uniform thickness over its entire surface, significantly different printing pressures, i.e., the pressure at which the ink is transferred from the image areas of the plate to the sheet 11, will result. It is a fact that a relatively slight change (and what might be considered insignificant by those not conversant with this art) in the effective diameter of the printing form can result in changes in the printing pressure which are significant.

Where the same pressure of the inked plate against the print receiving material 11 is to be maintained in the case of each of the plates, it will be necessary to make a corresponding proportionate change in the height of the tympan material on the impression cylinder 12. Therefore, the section of the tympan corresponding to the light form plate 25a is shown raised, or packed, a corresponding amount to the decrease in packing under that plate, and the section of the tympan corresponding to the heavy form plate 25b is lowered, as by decreasing its packing proportionately in the same manner. This will result in equality of transfer of the ink image from each plate to the sheet material. The necessary change in height of the tympan sheet can be accomplished with any of the same constructions and arrangements as described with reference to the different packing of different parts of the inking member. If different pressures are desired from different ones of the plates, then proportionate or appropriate changes in the packing of the tympan sheet with respect to any corresponding plate can be made according to known make-ready procedures.

FIG. 5 is a partial sectional view on a greatly enlarged scale, illustrating the manner in Which the plate 25a is packed, and likewise the tympan on the impression cylinder is adjusted in thickness in a corresponding manner.

FIG. 4 shows, in schematic fashion, an exaggerated short and long image obtained from the plates 25a and 25b respectively when packed to the same height. The dot-dash lines 54 are merely for the purposes of'delineating between the two relatively different images and also to provide a base or comparison average image length. It will be understood that this illustration is merely for purposes of explanation, since the relationships are all relative. Thus, the image 55a is seen to be longer than average, while the image 55b is shorter than average.

In accordance with the invention, referring to FIGS. 5 and 6, the plate 25a is placed over packing 60a which may be of variable thickness, as by using layers of differing thickness, or by using multiple layers of the same thickness. By building up the thickness of the packing beneath the plate 25a, it is thus possible for the pressman to control and adjust the length of the print from the plate 25a for example by shortening the length of the image 55a until it approaches the average length indicated by the lines 54. At the same time the tympan sheet 15 on the impression cylinder 12 can be adjusted by placing suitable packing 62 therebeneath, in exactly complementary fashion to the packing 60a if uniform printing pressure is desired. The image length is shortened by increasing the packing under the plate, which, by increasing the cylinder diameter, presents the outer printing surface slightly nearer its flat, true length. It has been found that a change of .001 in packing under the plate will effect from .006" to .008" change in print length on a cylinder having a diameter of approximately 10 inches. The change effected in print length will vary depending on such factors as stock printed, printing pressure required, ink used, etc.

In like manner, the plate 2511 (FIG. 6) can be packed, by packing 60b, to a lesser extent than plate 25a, i.e., less thickness of packing is used. This tends to lengthen the print or image 55b since the plate will be bent around a smaller radius and the outer surface of the plate will effectively stretch more than previously. It will be obvious that by proper correlation of the packings 60a and 60b the length of print from both the light form plate 25a and the heavy form plate 25b can be brought to the same length, if desired, or topredetermined different lengths which are in register with impressions obtained from a plate in another color, either in a different section of a multi-color press, or from a separate impression made in the same press. Also, in similar fashion, as shown in FIG. 6, the packing 63 beneath the tympan sheet 15 is greater than the packing 62, by an amount corresponding to the difference in thickness between the packings 60a and 60b, assuming as noted that the same printing pressure is desired from each plate.

As mentioned, to maintain proper and uniform pressure at the inking nip 48, different packing must be used between the different areas or sections of the resilient inking member or blanket 40. Thus, referring to FIG. 7, that part of the blanket 40 which inks the plate 2511 will have packing 65 which is of less thickness than the packing 66 under that part of the blanket which inks the plate 25b. Therefore, the same pressure and interference of the resilient inking member 40 is attained between the plates and blanket in each instance, and each plate is inked uniformly and correspondingly.

Because of the above described difference in thicknesses of packing as between the different plates, it is necessary to have separate clamping and tensioning means for each plate, for example leading and trailing edge clamps 22a and 2212, such that (the tension in each plate, and the alignment of each plate, can be adjusted separately from the other. Of course, provisions may be made for handling any number of plates on the plate cylinder, and the differences in packing to adjust the length of print from each plate or form will be carried through in like manner as to packing each plate and the corresponding areas of the inking member.

FIG. 9 is a graph showing typical variations in length of print produced by differences in packing beneath a heavy form or plate (i.e., relatively large image area) and a light form or plate (lesser image area). The lines representing these two plates are labeled accordingly. The central horizontal line of the graph represents zero or average print length, and changes in print length are indicated on the y axis above or below zero. For purposes of illustration only, a total thickness of a standard or average plate and packing, packed to bearer height, is chosen as 0.038 inch. This value is represented by a vertical line at the center of the graph, and it will be obvious that increases and decreases in this total thickness are indicated to the right and left of this line on the base line of the graph. It should be understood that this particular graph is merely for purposes of example herein, and will not necessarily correspond to actual plates, since there will be one or more curves or lines prepared for any plate, and different types of plates, paper, and numerous other variables also affect the result.

Referring to the graph, the line representing print length of a light form packed to bearer height (0.038 inch indicates a print length in excess of normal of about 0.020 inch, while the heavy form packed to the same height gives a print length of about 0.020 inch less than the average. The print lengths can be equalized, for example, by increasing the packing under light form and decreasing the packing under the heavy form until the same print length is obtained. If the total plate and packing height of the heavy form is made 0.035 inch, and the light form is packed until the thickness of the plate and packing equals 0.041 inch, then an average print length will be obtained from each plate, and of course the print length will be the same from each. Whether or not packing under one plate or both will be varied to produce the desired result will depend upon whether a proper and undistorted print can be obtained from both plates when their print length is made equal.

Also, as mentioned, it is likely that the print length may need to be adjusted such that different colors from different impressions are in register, and the length of print from the split plates on the same cylinder may be purposely different. This is especially advantageous in multi-color printing involving half-tones, where the half-tone dots must be maintained in the same relative position (i.e., adjacent, or overlapping, or superimposed) throughout the multi-color print in order to avoid a change in hue of a given color in different parts of the print.

Accordingly, the present invention provides a novel method and novel apparatus for adjusting the print length produced by thin flexible letterpress plates, while maintaining a high quality print. The requisite changes in packing can be accomplished readily, and by techniques already known to those in the art for other purposes, thus it is possible to obtain accurate register while conserving on the number of impressions or runs through the press, and the number of impressions required to produce a composite or multi-color image can be considerably reduced, according to the number of plates that can be mounted on the same cylinder and printed from simultaneously.

It should be noted that, depending upon the requirements of a particular job, the practice of the present method may involve no use of packing under one or more of the printing plates, and under a portion or all of the inking blanket. The invention provides for convenient and accurate adjustment of the length of print, but other known make-ready operations may also be involved, such as spot-packing particular areas of the tympan to obtain an even print. Thus, it is possible that the packing beneath areas of the inking blanket and areas of the tympan which cooperate with corresponding areas of the same plate may or may not be equal in thickness. The packing beneath the blanket, however, will be of a thickness corresponding (inversely) to the packing beneath the plate, as outlined previously, although variations may be introduced in the packing beneath the tympan for make-ready purposes. It should be noted also that in some circumstances different plates mounted on the same plate cylinder may be of different thickness, and of course it may be necessary to take this into account when packing beneath the plates to adjust to the desired length of print. Therefore, the examples given and illustrated on the graph in the drawings, are designated in terms of total thickness of the plate and its packing, or in other words the total height of the type surface with respect to the surface of the plate cylinder.

While the method disclosed preferably contemplates the use of the split plate arrangement, it is sometimes possible to employ the concept of differential packing using only one plate. In such a case, the plate should be such as to enable some stretching at the line where the packing height differs. Additionally, it is preferable not to print immediately adjacent this line in a single plate arrangement. This concept is intended to be included in certain of the broader claims.

While the method and form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise method and form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In a letterpress having an inking cylinder, a plate carrying member and an impression cylinder arranged to carry print receiving material into contact with plates on said plate carrying member, the combination of a resilient inking member covering the effective inking surface of said inking cylinder, means for applying an essentially uniform layer of ink over the surface of said inking member, means on said piate carrying member for mounting a plurality of plates in side by side relation, relief plates on said plate carrying member effective to print on different areas of a print receiving material and each of said plates .having image areas substantially different in extent providing at least one heavy form and one light form from which predetermined print length on said print receiving material is desired, said mounting means including a plurality of individually adjustable plate clamps holding both the leading and trailing edge areas of each plate to provide for individual adjustment of each said plate on said plate carrying member, packing beneath said plates varying in thickness as between said plates with thicker packing under said light form and thinner packing under said heavy form, correspondingly varying thickness packing beneath said inking member on said inking cylinder cooperating with the differentially packed said printing plates to maintain proper application of ink to said plates, and tympan means on said impression cylinder, said tympan means being of different thickness according to the areas thereof contacting respective ones of said plates to maintain proper printing pressure between each of said plates and the print receiving material.

2. In a rotary printing press of the letterpress type having an inking cylinder and a plate cylinder of the same diameter and an impression cylinder arranged to carry print receiving material through a nip between the plate cylinder and the impression cylinder, the combination of a resilient inking member covering the effective inking surface of said inking cylinder, a plurality of form rolls for applying an essentially uniform layer of ink over the surface of said inking member, means on said plate cylinder for mounting a plurality of plates in side by side relation, a plurality of thin flexible printing plates having essentially shallow relieved non-image areas, each of the ing in thickness as between said plates in accordance with 9 the predetermined lengths of print desired from the image area to be reproduced from each plate, and correspondingly varying tympan means on said impression cylinder cooperating with the differentially packed said printing plates to accommodate the difference in length of print resulting from the characteristics of said plates.

3. A rotary letterpress adapted to use thin flexible relief plates, comprising an inking cylinder, a resilient inking blanket of substantially uniform thickness mounted on said inking cylinder, means for applying an essentially uniform coating of ink to the surface of said blanket, a plate cylinder having the same diameter as said inking cylinder and mounted next to said inking cylinder defining therewith a nip across which ink is transferred, a plurality of relatively thin flexible relief printing plates mounted to extend in side by side relation on said plate cylinder and to receive ink on the non-relieved image areas thereof from said blanket by reason of controlled pressing of said blanket against said plates at said ink transferring nip, bearers on said inking cylinder and on said plate cylinder running in contact during printing operation to control the impression of said blanket against said plates, packing beneath each of said plates graduated differentially to arrange the irnage areas of said plates at slightly different heights with respect to the surface of said plate cylinder in accordance with characteristics of the image areas on the respective plates, corresponding packing beneath said inking blanket to maintain proper ink transferring relationships between said blanket and the image areas of said plates, separate individually adjustable clamp means on said plate cylinder engaging both the leading and trailing edges of each said plate providing for independent adjustment of the tension and placement of said plates on said plate cylinder, an impression cylinder displaced about the circumference of said plate cylinder from said inking cylinder and defining with said plate cylinder a printing nip through which print receiving material is passed to transfer ink from the image areas of said plate onto said material forming the desired printed image thereon, and tympan means on said impression cylinder of predetermined dilferent thickness according to the height of the image areas of the respective plates to control the pres sure with which the print receiving material is forced against each of said plates to secure the desired length of print from each of said plates.

4. A rotary letterpress adapted to use thin flexible relief plates, comprising an inking cylinder, a resilient inking member mounted on said inking cylinder, means for applying an essentially uniform coating of ink to the surface of said inking member, a plate cylinder mounted next to said inking cylinder defining therewith a nip across which ink is transferred, a plurality of relatively thin flexible relief printing plates including at least one relatively heavy form and a substantially lighter form mounted in side by side circumferential extent on said plate cylinder receiving ink on the non-relieved image areas thereof from said inking member by reason of controlled pressing of said inking member against said plates at said ink transferring nip, packing beneath each of said plates graduated differentially between said heavy form and said lighter form to arrange the image areas of said plates at slightly different heights with respect to the surface of said plate cylinder in accordance with the predetermined length of print from the respective plates, corresponding packing of inverse different thickness beneath the areas of said inking member arranged tocontact the respective said plates for proper inking of each said plate, separate individually adjustable clamp means on said plate cylinder engaging both the leading and trailing edges of each said plate providing for independent adjustment of the tension and placement of said plates on said plate cylinder, an impression cylinder displaced about the circumference of said plate cylinder from said inking cylinder and defining with said plate cylinder a printing nip through which print receiving material is passed to transfer ink from the image areas of said plates onto'said material forming the desired printed image thereon, and tympan means of correspondingly differential thickness carried on said'impression cylinder to control individually the pressure by which the print receiving material is forced against each said plate to secure the desired length of print from each of said plates.

5. The method of controlling the length of print obtained from a thin flexible relief printing plate in a relief printing press having a plate carrying member wherein the plate is divided lengthwise into at least two different form areas having significantly different percent of image to non-image printing areas, an impression cylinder forming a printing nip with said plate carrying member, and an inking cylinder having a resilient inking surface for inking a plate on said member; comprising the steps of:

(a) independently adjusting the height of each entire image area of the plate with respect to the supporting surface of the Plate carrying member while maintaining the mechanical operating relationship between the plate carrying member and the impression cylinder and thereby adjusting the length of print obtained from each form area of the plate to a desired length,

(b) adjusting the height of said inking surface with respect to each form area of the plate correspondingly and in inverse fashion to obtain proper transfer of ink onto the image areas only of each form area of the plate, and

(0) providing a tympan member on said impression cylinder which is raised with respect to the surface of said impression cylinder by an amount sufficient to provide proper transfer of ink from each form area of the plate to print receiving material passed through said printing nip.

6. The method of controlling the length of print obtained from each of a plurality of thin flexible relief plates mounted on the same plate carrying member of a printing press, said press having an impression cylinder forming a printing nip with said plate carrying member and an inking cylinder -with a resilient inking surface arranged to apply ink to a plateon said member; comprising the steps of (a) separately adjusting the height of the entire image area of each said plate with respect to the supporting surface of the plate carrying member, as by packing beneath the individual said plates, and thereby adjusting the length of print obtained from each said plate to predetermined print lengths desired from the individual plates,

(b) providing a tympan on said impression cylinder having a thickness in the areas corresponding to each plate of an amount sufficient to provide proper transfer of ink from the image areas of each plate onto print receiving material passed through said printing nip, and

(c) adjusting the height of entire areas of said inking surface corresponding to each said plate with respect to said inking cylinder in inverse relation to the height at which the plate corresponding to such area has been raised to obtain proper transfer of ink onto the image areas only of each plate.

7. The method of controlling the length of print obtained from each of a plurality of thin flexible relief plates mounted in side by side relation on a plate cylinder of a rotary relief printing press, said press having an impression cylinder forming a printing nip with said plate cylinder and an inking cylinder forming an inking nip with said plate cylinder, said inking cylinder having a resilient inking blanket to cover the entire active inking areas of the inking cylinder; comprising the steps of (a) separately adjusting the height of the entire image area of each said plate with respect to the supporting surface provided by the plate cylinder while main- 1 1 l. 2 taining the mechanical spacing between the axes of to such areas have been raised to obtain proper transrotation of said plate cylinder and said impression fer of ink onto the image areas only of each plate. cylinder and thereby adjusting the length of print obtained from each plate to a predetermined print References Cited in the file of thls Patent length desired from that plate, 5 UNITED STATES PATENTS (b) providing a tympan member on said impression I 135179 Hamilton A r 13 1915 cylinder having the areas thereof corresponding to 2002814 Harrow a 1935 each plate adjusted by an amount suflicient to pro- 2O36'835 Sites 1936 vidt;1 prtiper transfer of ink from the image areas of 3O25792 g h 1962 eac p ate onto print receiving material passed 10 n through Said printing nip, and Downle (c) adjusting the height of areas of said inking blanket OTHER REFERENCES With respect to Said inking cylinder in inverse rela- Kuehn, Albert T. True Rolling on Offset Presses, May

tion to the height at which the plates corresponding 1 1952 

5. THE METHOD OF CONTROLLING THE LENGTH OF PRINT OBTAINED FROM A THIN FLEXIBLE RELIEF PRINTING PLATE IN A RELIEF PRINTING PRESS HAVING A PLATE CARRYING MEMBER WHEREIN THE PLATE IS DIVIDED LENGTHWISE INTO AT LEAST TWO DIFFERENT FROM AREAS HAVING SIGNIFICANTLY DIFFERENT PERCENT OF IMAGE TO NON-IMAGE PRINTING AREAS, AN IMPRESSION CYLINDER FORMINA A PRINTING NIP WITH SAID PLATE CARRYING MEMBER, AND AN INKING CYLINDER HAVING A RESILIENT INKING SURFACE FOR INKING A PLATE ON SAID MEMBER; COMPRISING THE STEPS OF: (A) INDEPENDENTLY ADJUSTING THE HEIGHT OF EACH ENTIRE IMAGE AREA OF THE PLATE WITH RESPECT TO THE SUPPORTING SURFACE OF THE PLATE CARRYING MEMBER WHILE MAINTAINING THE MECHANICAL OPERATING RELATIONSHIP BETWEEN THE PLATE CARRYING MEMBER AND THE IMPRESSION CYLINDER AND THEREBY ADJUSTING THE LENGTH OF PRING OB- 